She told ET she was "just checking in on her, and congratulating her on her marriage. Or her pending marriage."
"I love her," she added.
Speaking with Access Hollywood at the same event, Madonna echoed her sentiment about Britney's engagement to Sam Asghari, saying, "So happy for her, love her to death."
Earlier this month, Britney announced the good news by sharing a clip of her and Sam showing off the sparkler he gave her in an Instagram post, with the caption, "I can't f------ believe it 💍💍💍💍💍💍❣️!!!!!!"
"How the conservatorship has controlled her life has never been revealed," added the statement. "Now, in this New York Times investigation, a portrait emerges of an intense surveillance apparatus that monitored every move she made."
Both "Controlling Britney Spears" (which debuts tonight on Hulu and FX) and "Britney vs. Spears (which debuts on Netflix September 28) arrive before the next court hearing in Spears' conservatorship case. On September 29, a judge is expected to hear Britney's request to have Jamie removed from the conservatorship, as well as Jamie's recent petition to end the conservatorship.